<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style type="text/css">
			.father{
				width: 100px;
				height: 100px;
				background-color: #00FFFF;
				margin-top: 100px;
			}
			.son{
				height: 100px;
				margin: 0 -20px;
				background-color: #CCCCCC;
			}
		</style>
	</head>
	<body>
		<!-- 普通元素 -->
		<div class="father">
			<div class="son"></div>
		</div>
	</body>
</html>
